Minimally invasive, percutaneous procedures have a wide variety of applications in medical diagnosis and therapy. Biopsy, delivery of localized therapy, and anesthesia are performed quickly and with minimal patient trauma using long, fine needles to access the desired site within the body via a puncture from the skin surface.
A significant factor limiting the success of minimally invasive, percutaneous procedures is the limited degree of control available to the operator over the path of the needle. Once the needle tip has pierced the skin along the chosen axial trajectory, the operator has direct control only over insertion depth. Choosing the correct insertion angle is itself challenging but compounding this difficulty is the tendency of fine needles (typically 20-22 gauge) to wander laterally from the insertion axis as the needle advances through the patient's tissue. This lateral wandering effect is caused by several factors including the bevel cut faces of the needle, inhomogeneous tissue properties such as friction and elasticity, and unintentional lateral forces applied to the needle base by the operator's hand. We have observed in the laboratory that these effects can noticeably bend the needle away from its apparent axis at the base resulting in a missed target and the need to perform a second insertion. This effect has also been observed in clinical practice, even under real-time image guidance. For example, see the article “US-guided nephrostomy with the aid of a magnetic field-based navigation device in the porcine pelvicaliceal system”, Krombach G A, Mahnken A, Tacke J, Staatz G, Haller S, Nolte-Ernsting C C A, Meyer J, Haage P, Gunther R W, Journal of Vascular and Interventional Radiology, 12 (5), pp. 623-628, May 2001.
Many biopsies, however, require fluid or cell samples for diagnosis by a pathologist. For these cytological biopsies, fine needles are normally used. Other procedures such as amniocentesis involve direct suction from fluid cavities in the body and similarly require the use of fine needles often at depths exceeding 10 cm.
An additional limitation to the success of percutaneous needle procedures is the presence of bones, major blood vessels, nerves and other sensitive features in the body that may not leave a straight-line access to the target. In such instances, minimally invasive needle procedures are generally not possible and the physician may then have to resort to surgery.
The desire to access targets that reside laterally from the available insertion trajectory is evident in many recent US patents. McGuckin et al., in U.S. Pat. No. 6,425,887, describe a system consisting of a large outer cannula containing many smaller needles inside. Advancing the inner needles causes them to exit the outer cannula laterally in all directions. Schroeder et al., in U.S. Pat. No. 6,228,049, describe a needle introducer with a laterally inclined exit hole such that a flexible needle may be inserted through the introducer to access lateral target sites. Racz et al., in U.S. Pat. No. 6,146,380, describe a surgical probe with a rigid, bent tip to allow steering freedom inside the body. Finally, several patents describe catheters that allow a lateral degree of freedom at the tip. U.S. Pat. Nos. 6,217,554 and 6,190,353 describe catheters in which a needle inserted through the catheter exits the tip with a strong lateral curve, and in U.S. Pat. No. 5,345,937, Middleman et al. describe a system allowing the tip of the catheter cannula to be bent in any desired direction to aid in navigating the blood vessels.
None of these patents provides the equipment or methodology to variably steer a medical needle during its insertion. U.S. Pat. Nos. 6,425,887, 6,228,049, 6,217,554, and 6,190,353 cited above only provide methods of lateral access to target sites from traditional access routes, by a straight-line needle insertion or catheter blood-vessel navigation. This prior art does not describe how to steer a needle during insertion to generate a prescribed path.
U.S. Pat. No. 6,146,380 describes steering a surgical probe with a bent tip, but the curvature of the tip is fixed which allows the physician to control steering direction but not magnitude, and the probe does not track straight.
U.S. Pat. No. 5,345,937 describes a catheter steering system suitable for aiding in navigating branching blood vessels with a flexible catheter tube, but this system cannot steer fine, stiff needles through the body's flesh.
None of the existing systems provides motorized or computer-controlled actuation of the needle components nor do they provide visual feedback to aid in the physician's understanding and visualization of the needle and target positions inside the body.
Larger needles (18 gauge or less) are usually stiff enough that they do not wander off the axis during insertion, but these needles are generally used in core biopsies when solid tissue samples are required.